The linear motors have been frequently used as driving sources of a linear actuator that linearly moves goods or members in an FA device such as an X-Y table or a goods carrier device. A so-called linear motor actuator using a linear motor is generally composed of a guide table on which a movable body such as goods to be carried is mounted, a linear guide device that makes the guide table linearly reciprocatable, a linear motor that applies a thrust force to the guide table, and a linear encoder that detects a position of the guide table. The linear actuator controls the linear motor according to a detection value of the linear encoder, thereby making it possible to give the guide table an arbitrary movement with high precision (JP-A 2002-136097).
As the linear motor, there has been known a structure in which a field magnet that acts as a stator in which N magnetic poles and S magnetic poles are alternately arranged is disposed on a base plate, a forcer that acts as a movable element is disposed on a lower surface side of the guide table that is supported by the linear guide device, and the field magnet and the forcer face each other with a slight gap therebetween.
However, in the case where the field magnet is disposed on the base plate, it is necessary to dispose the guide table so as to cross the field magnet in order that the forcer and the field magnet face each other. In addition, it is necessary that a pair of linear guide devices are disposed on both sides of the field magnet to support linear reciprocation of the guide table, which leads to a tendency to enlarge the structure itself of the actuator.
On the other hand, as another type of the linear motor, there has been known a so-called rod type (JP-A 11-150973). The linear motor of the rod type is composed of a magnet rod that acts as a stator which is rod-shaped, has N poles and S poles repetitively arranged along an axial direction thereof, and has both ends supported on the base plate, and a forcer into which the magnet rod is loosely inserted with a slight gap therebetween. The linear motor is configured such that a coil member that is disposed within the forcer is energized, thereby making the forcer move around the magnet rod along the axial direction.
In the linear motor of the rod type, since the coil member surrounds the magnet rod, it is possible to exercise a strong thrust force. In the case where the linear motor of this type is used to configure the actuator, it is possible to give a large thrust force to the guide table while the actuator is downsized. Also, the linear guide device that supports the reciprocation of the guide table is generally composed of a track rail that is disposed on the base plate, and a slider that moves along the track rail. However, in the rod-type linear motor, it is possible to employ a so-called built-up structure in which the forcer is fixed to the slider, and the guide table is further fixed onto the forcer. Therefore, the rod-type linear monitor has such a characteristic that the actuator itself is readily downsized as compared with the type using a biaxial linear guide device as with the linear motor actuator disclosed in JP 2002-136097.
Patent Document 1: JP 2002-136097 A
Patent Document 2: JP 11-150973 A